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Biomedical subjects

R Weber

Publications and source records attributed to R Weber.

At least 343 records · Page 19Linked to original sources
PubMed1988

[Chronic formaldehyde exposure--a misunderstood disease?].

A family with chronic exposure to formaldehyde in a renovated apartment is reported. The source of exposure proved to be chipboard. The family members' symptoms were eye and upper airway irritation, malaise, headache, nausea, sleeping disturbances, irritability and lack of appetite. At first the syndrome was thought to be psychosomatic and the correct diagnosis was overlooked. Ten years after beginning of the chronic exposure a formaldehyde level of 0.35 ppm was still recorded in the apartment. Sources, symptoms and diagnosis of chronic formaldehyde immission are discussed.

Adult↗
PubMed1988

[A method for the determination of ergot alkaloids in food].

A suitable method has been developed for the routine analysis of the ergot alkaloids ergometrine, ergometrinine, ergosine, ergosinine, ergotamine, ergotaminine, ergocornine, ergocorninine, alpha-ergocryptine, alpha-ergocryptinine, beta-ergocryptine, beta-ergocryptinine, ergocristine and ergocristinine in cereal products. The method consists of food extraction, cleaning of the crude extract by a modified form of the Extrelut method, and identification and quantitative determination of the alkaloids by high pressure liquid chromatography (HPLC). The results are confirmed by thin layer chromatography (TLC) and gas-chromatography/mass spectrometry (GC/MS). Market investigations have shown contaminations in ecological as well as in conventional products, with rye products mainly being contaminated. Within the EEC, a maximum value of 0.05% ergot respectively a total alkaloid content of 1 mg/kg in cereals used for food production is prescribed. This value was not exceeded in any of the investigated samples.

Chromatography, High Pressure Liquid↗
PubMed1988

[Food contamination by emissions from dry cleaning compounds].

Tetrachloroethene (perchloroethylene) from dry-cleaning units may contaminate adjacent flats in the same building. Increased concentrations of tetrachloroethene have been found in foodstuffs in homes situated above dry cleaning units and in foodstuffs from groceries located neat drycleaning units. The concentrations were extremely high in foods rich in fat.

Air Pollutants, Occupational↗
PubMed1988

[Chemical and toxicologic studies of native corn in flour and bread].

During the bread-baking process, total alkaloid content is reduced by about 50%, the pharmacologically active alkaloids (the '-in' types) being reduced to a much greater extent than the less active type ('-inin' type). Using ergotamin and ergokryptin as a basis, total alkaloid levels were calculated from the HPLC data; these results were in a good agreement with the total alkaloid content calculated from 13 individual ergot alkaloids. The changes in the alkaloid spectrum caused by pelletin are shown. In feeding experiments with growing, pregnant, and lactating mice, diets with 0%, 1% and 2% unbaked (MM) or baked (MB) rye ergot were compared for possible toxic effects on reproduction, using animals fed ad libitum or pair-fed controls. A mean ingestion of 3.6 mg of alkaloids/kg body weight per day (MM 2%) was maternally toxic and caused inhibition of conception and implantation. Feeding with 1.3 or 1.6 mg of alkaloids/kg body weight per day (MM 1% and MB 2%) during pregnancy had no significant toxic effect on the embryo or fetus, but resulted in gestation time being prolonged to about 10 h. During lactation, an intake of 2.9 and 3.0 mg of alkaloids/kg body weight per day (MM 1% and MB 2%) led to a considerable reduction in growth (up to 50%) in the young mice compared to the control animals fed ad libitum. Both the determination of total ergot alkaloid content and the feeding experiment indicate that the bread-baking process causes a reduction and consequently a detoxification of ergot alkaloids of about 50%.

Abnormalities, Drug-Induced↗
PubMed1988

Radiation therapy for carcinoma of the nasal vestibule.

From 1963 to 1984, 32 patients with squamous cell carcinoma of the nasal vestibule received definitive radiation therapy. Of these, 11 patients whose superficial lesions were suitably located received radium implants, and the other 21 patients were treated with a combination of electron beam and 60Co. The implant doses ranged from 60 to 75 Gy and the external beam doses ranged from 55 to 70 Gy. In 12 patients, the submandibular and subdigastric nodes were electively treated with 60Co with doses of 45 to 50 Gy, and in 12 patients the strip of skin between the nose and the free border of the mandible was also electively irradiated. None of the 11 patients treated by interstitial implant experienced treatment failure. In the 21 patients treated by external beam, one patient had primary tumor recurrence and four patients failed in the unirradiated neck. A metastasis developed in the unrradiated tissues between the nose and the neck on the only patient who died of the disease. Necrosis of the anterior art of the upper jaw of one patient developed as a result of a hot spot. Today, when treatment is calculated with the help of a computer program and special techniques to optimize tumor dose, hot spots can be prevented.

Adult↗
PubMed1988

[Determination of aflatoxin B1 in dried figs by visual screening, thin-layer chromatography and ELISA].

Aflatoxin B1-contaminated fruits were sorted out from 250 kg dried figs (five Turkish and three Greek batches) by bright-greenish-yellow fluorescence under UV light. The aflatoxins of the fluorescent figs were extracted by simple soaking in methanol. Aflatoxin B1 was determined by thin-layer chromatography. Parallel to this, an extraction for the determination of aflatoxin B1 was developed by a competitive ELISA and the two methods were compared with each other. In a highly contaminated batch of Turkish figs, statistically there was one fig among 350 which had a high aflatoxin content (greater than 100 ng/g fig) and one fig amongst 140 fruits with an aflatoxin B1 content of greater than 10 ng B1/g fig.

Aflatoxin B1↗
PubMed1987

[Contamination of foodstuff by gases from tetrachloroethene emissions from a dry cleaners].

Tetrachloroethene (perchloroethylene) and other volatile organic compounds may contaminate the surroundings of dry-cleaning units. Increased concentrations of tetrachloroethene were found in food, human hair, textiles and dust from a vacuum cleaner in a home situated above a dry-cleaning unit. The concentrations were found to be extremely high in food rich in fat. The analytical procedure for the above-mentioned samples is described.

Air Pollutants↗
PubMed1987

Monoclonal antibody Tor 23 recognizes a determinant of a presynaptic acetylcholinesterase.

A significant proportion of the acetylcholinesterase that is present in the electric organ of Torpedo californica exists as a presynaptic membrane molecule. The monoclonal antibody Tor 23 binds the Torpedo presynaptic nerve membrane where it recognizes a polypeptide of 68,000 daltons. Our present studies indicate that Tor 23 identifies acetylcholinesterase. From the homogenates of Torpedo nerve terminals, Tor 23 immunoprecipitates measurable esterase activity. Esterase precipitation was not observed with no Tor 23 added; nor was it observed with any other test antibodies, including other Tor antibodies, in particular, Tor 70, which binds, as does Tor 23, to the presynaptic nerve membrane. The esterase activity was specific for acetylcholinesterase. Our studies indicate the molecule defined by Tor 23 has the solubility properties described for that of presynaptic acetylcholinesterase: it is soluble in detergent-treated electroplax homogenates and insoluble in high-salt extractions. In sections of Torpedo back muscle, both nerve and endplate acetylcholinesterase can be detected histochemically. Tor 23 localizes to the nerve and is not clustered at the endplate. The utility of the antibody Tor 23 thus includes biochemical and histological analyses of the multiple forms of acetylcholinesterase.

Acetylcholinesterase↗
PubMed1986

The Cpx proteins of Escherichia coli K12. Immunologic detection of the chromosomal cpxA gene product.

Previous studies described lacZ'- and cat'-'cpxA fusion genes whose expression restored to normal all the phenotypic defects associated with cpxA mutations (Albin, R., and Silverman, P. M. (1984) Mol. Gen. Genet. 197, 272-279). Here, we show by DNA nucleotide sequence analysis that the fusion genes encode 241 carboxyl-terminal amino acids of the CpxA polypeptide. Using this information, we constructed a fusion gene containing the same 241 cpxA codons preceded by 1007 codons of beta-galactosidase. The resultant hybrid polypeptide was purified and used to raise an anti-(CpxA polypeptide) antiserum. Using the antiserum, we have identified the chromsomal Escherichia coli K12 cpxA gene product as a 52-kDa polypeptide. The polypeptide showed temperature-sensitive accumulation in a strain carrying both the cpxA2[Ts] and cpxB1 alleles and accumulated to a level higher than normal in cells that carried a high-copy number, cpxA+ plasmid. Immune precipitates of in vitro transcription-translation reactions with cpxA+ plasmids as template also contained a 52-kDa polypeptide, indistinguishable in electrophoretic mobility from the immunoreactive polypeptide synthesized in vivo. Two regions of amino acid sequence at the carboxyl-terminus of the CpxA polypeptide are significantly homologous to corresponding regions of the E. coli K12 EnvZ polypeptide, an inner membrane component that, like the CpxA polypeptide, is required to maintain the protein composition of the cell envelope. The cpxA coding sequence is followed by two repetitive extragenic palindrome sequences in opposite orientation.

Amino Acid Sequence↗
PubMed1986

Conserved sequences and cell-specific DNase I hypersensitive sites upstream from the co-ordinately expressed alpha I- and alpha II-globin genes of Xenopus laevis.

The globin gene family of Xenopus laevis comprises pairs of closely related genes that are arranged in two clusters, each pair of genes being co-ordinately and stage-specifically expressed. To get information on putative regulatory elements, we compared the DNA sequences and the chromatin conformation 5' to the co-ordinately expressed adult alpha-globin genes. Sequence analysis revealed a relatively conserved region from the cap site up to position -289, and further upstream seven distinct boxes of homology, separated by more diverged sequences or deletions/insertions. The homology boxes comprise 22 to 194 base-pairs showing 78 to 95% homology. Analysis of chromatin conformation showed that DNase I preferentially cuts the upstream region of both genes at similar positions, 5' to the T-A-T-A and the C-C-A-A-T boxes, only in chromatin of adult erythroblasts and erythrocytes, where adult globin genes are expressed, but not in chromatin of adult liver cells or larval erythrocytes, where these genes are silent. This suggests that cell- and stage-specific activation of these genes coincides with specific changes in chromatin conformation within the proximal upstream region. No difference was found in the nucleotide sequence within the DNase I hypersensitive region proximal to the adult alpha 1-globin gene in DNA from embryonic cells, in which this gene is inactive, and adult erythrocytes, expressing this gene.

Animals↗
PubMed1986

Sequence analysis of the larval beta II-globin gene of Xenopus laevis.

The 1822 bp sequence of the larval Xenopus laevis beta II-globin gene is reported together with 240 bp upstream of the gene and 190 bp beyond the site of polyadenylation. The mRNA start point was determined by primer extension as well as nuclease S1 mapping and the polyadenylation site by comparison of the gene sequence to the mRNA sequence derived from a corresponding cDNA clone. Like other vertebrate globin genes, this gene comprises three exons interrupted by two intervening sequences (IVS). IVS I spans over 582 nucleotides and interrupts the exon sequences within codon 30. IVS II is located between the codons 104/105 and spans over 617 nucleotides. The 5' region of the gene contains the canonical TATAA homology at position -31. Comparison of the upstream sequence to that of Xenopus laevis larval beta I-globin gene revealed a conserved sequence, located between nucleotide positions -60 and -87, which might function as regulatory element of transcription. Whereas the upstream region of the larval beta II-globin gene does not contain a CAAT box, we notice a reiterated AAATGA motif and discuss its possible significance.

Amino Acid Sequence↗